The proposed project will investigate the ontogenetic development of latent inhibition in the rat. The habituation to the novel stimulus will be presented at various ages ranging from 21 days to 60 days of age. Subsequent to habituation or control procedures, the CS will be paired with electrical shock and the resulting suppression of drinking will be used to assess the rat's inhibitory abilities. The results are expected to contribute substantially to our understanding of the postnatal development of inhibitory behavior.